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Since pre-industrial times OH changed by :

Since pre-industrial times OH changed by :. +7 % [Berntsen et al.. JGR, 1997; Martinerie et al., JGR,1995]. - 9 % [Wang and Jacob, JGR, 1998]. -15 % [Lelieveld and Dentener, 2000]. Van Aardenne et al. (GBC, 2001). Since pre-industrial times OH changed by :.

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Since pre-industrial times OH changed by :

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  1. Since pre-industrial times OH changed by: • +7 % [Berntsen et al.. JGR, 1997; Martinerie et al., JGR,1995] • - 9 % [Wang and Jacob, JGR, 1998] • -15 % [Lelieveld and Dentener, 2000]

  2. Van Aardenne et al. (GBC, 2001)

  3. Since pre-industrial times OH changed by: • +7 % [Berntsen et al. JGR, 1997; Martinerie et al., JGR, 1995] • - 9 % [Wang and Jacob JGR, 1998] • -15 % [Lelieveld and Dentener, JGR, 2000] Recent methyl-chloroform inversions predict: • 15 ± 22 % for the period 1979-1989 (1.4 % year-1) • - 25 % for the period 1990-2000 (-2.3 % year-1) [Prinn et al., JGR, 2001; Krol and Lelieveld, JGR, 2002]

  4. What is the consistency of our knowledge on large scale • OH variability and trends in the period 1979-1993? • Changes in meteorology • Changes in anthropogenic emissions • Changes in stratospheric ozone • Why 1979-1993? • Meteorology from ECMWF-ERA15 re-analysis used by global CTM TM3 • Emissions from EDGAR/Historical Emission database • CH4 from surface network • Stratospheric O3 from TOMS

  5. Experiments: • Varying meteorology and photo-chemistry 1979-1993 • Fixed meteorology (1993), varying emissions • Varying meteorology and constant emissions • … in total eight combinations …. • Analyze OH changes as CH4 lifetime.

  6. O3 [ppbv] at earth surface: simulated-measurements 1979-1993 Measurement Model [Lelieveld and Dentener, JGR, 2000; Peters et al., JGR, 2000]

  7. CH4 emissions: Calculated - Edgar/HIS [Dentener et al., ACPD, 2002] Residual CH4 emissions: variability of natural emissions and unaccounted trends…. See poster [Dentener et al.]

  8. ECMWF Inter-annual variability of column moisture (1979-1993) 5 periods 50 40 30 20 10 5 0 10% 5% 0% -5% -10% BLUE: DRYGREEN-YELLOW: WET

  9. Change of anthropogenic emissions 1979-1993 (interpolated from van Aardenne et al., GBC, 2001)

  10. CH4 lifetime: full simulation-meteorology-chemical boundary conditions S1 base sim.[-0.24 ±0.06 % year-1] S2 Var meteo. [-0.20 ±0.09 % year-1 ] S3 Var Chem. [-0.02 ±0.05 % year-1 ] Multiple linear regression: 0.53-0.47, with high probability.

  11. CH4 lifetime:effect of humidity and scavenging on ‘meteorology simulation’ S2: Var. Meteo[-0.20 ±0.09 % year-1] S7: Var. Humidity[-0.13 ±0.09 % year-1 ] S8: Var. Scavenging [0.05 ±0.05 % year-1 ]

  12. CH4 lifetime:effect of emissions and photolysis rates on ‘chemistry only’ simulation S3: Var. Chemistry [-0.02 ±0.05 % year-1] S4: Var. TOMS [-0.15 ±0.05 % year-1 ] S6: Var Emissions [0.12 ±0.01 % year-1 ]

  13. Summary: • Many factors that control OH variability have been included in global • CTM with 15 years of real meteorology- as good as we can do it... • OH has been relatively stable during 1979-1993 [0.24 ±0.06 % year-1] • which does not support reports on strong OH changes. • Meteorological variability, and especially water vapor, explains most of the • variability and much of the calculated trend • Trends in stratospheric ozone increase OH, changes in surface emissions • decrease OH; effects cancel. • Computed OH variability probably underestimated since we did not assess • the role of variations in natural emissions (biomass burning!)

  14. CH4 lifetime:correlation of ‘chemical’ simulation and solar cycle Lifetime Solar cycle index Solar cycle index Lifetime Solar cycle index Lifetime

  15. O3 [ppbv] at earth surface: simulated-measurements 1979-1993 Average O3 seasonal cycle [ppbv] Measurement Model Model Stratosphere [Lelieveld and Dentener, JGR, 2000; Peters et al., JGR, 2000]

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